There are millions of cars and trucks on the roads today, used for both personal passenger transport and the movement of goods, most of which rely on fossil fuel for propulsion. In the case of standard tractor trailers, at highway speeds, aerodynamic drag is responsible for approximately half of the vehicle's fuel burn, meaning that even slight reductions in aerodynamic drag can result in a significant improvement in fuel economy and annual savings in fuel cost.
There are several physical areas on tractor trailers that account for the most significant portion of aerodynamic drag, and thus fuel usage. In the case of class 8 semi trailers, the more perpendicular and vertical front areas such as the radiator grill and windshield are significant, along with the gap between the tractor and trailer, as well as the rear doors. Even the mirrors, which are small relative to the overall vehicle size, contribute about 5% of the total drag of the vehicle, as their blunt shape is not aerodynamically efficient.
In addition, the rear tires of the trailer, also referred to as tandems, contribute significantly to the overall aerodynamic drag. In particular, during vehicle travel, the airflow under the trailer strikes the rear tires at nearly full speed and results in significant aerodynamic drag on the vehicle. Drag on the rear tires and undercarriage can account for approximately 10% of the total vehicle drag. In the case of tractor trailers and intermodal chassis trailers, the more perpendicular and vertical front areas such as the radiator grill and windshield area are significant, along with the gap between the tractor and container and rear container doors.
Existing solutions for reducing drag due to physical components under the trailer, namely, drag resulting from the rear tires, include the use of trailer skirts, which have become increasingly more common. The goal of such trailer skirts is to prevent airflow from entering the area under the trailer and impacting the rear tires, axles and brakes which, over the course of an average year of long haul driving, can be a significant contributor to fuel cost. Notably, however, trailer skirts can be quite costly and can be somewhat complex to properly install, at least partially negating the annual fuel cost benefit achieved by their use. In addition, commonly used skirts for standard semi-trailers are incompatible with intermodal chassis trailers and tankers due to the lack of a convenient place to mount the long, straight skirts.
In view of the above, there is a need for a simple, cost effective apparatus or device for reducing the aerodynamic drag of a vehicle, and more particularly, the drag associated with the rear tires, axles and brakes of a vehicle such as a tractor trailer, intermodal chassis trailer, tanker truck and the like.